嗜热L-乳酸高产菌株的选育

Breeding of efficient L-lactic acid producing thermophiles

采用高糖和平板快速筛选法从各种土壤、草料、温泉水中分离得到89株产乳酸的菌株,经过低糖与高糖的复筛,并结合高效液相色谱进行产物定量与光学纯度的检测,筛选到3株最适生长与发酵温度为50℃和55℃的L-乳酸高产菌S-18、S-32和S-44,该3株菌从100g/L葡萄糖出发,72h时产酸能力分别达到75.0g/L、81.9g/L和86.5g/L,光学纯度分别达到96.3%、96.6%和97.7%。对其中产量最高的S-44进行离子注入诱变,获得多株高产菌,其中Y-4从200g/L葡萄糖出发,产酸能力达到178.7g/L,对糖转化率达到89.4%,为进一步的开发奠定了基础。

L-lactic acid is the most useful organic acid. In this study, 89 strains producing lactic acid were isolated from soil, silage, hot spring water and surrounding soil. The concentration and enantiomeric purity of lactic acid produced by these strains were determined by HPLC. Based on the ability of the strains to produce L-lactic acid, three effective strains S-18, S-32 and S-44 which grew at 50℃ and 55 ℃ were selected. After 72 h of fermentation, 75.0 g/L, 81.9 g/L and 86.5 g/L of L-lactic acid were produced from 100 g/L glucose by the three strains, respectively. The enantiomeric purity of the products was 96.3%, 96.6% and 97.7%, respectively. Strain S-44 was mutated by the N^＋ion beam implantation, and more efficient mutants were obtained. By using the mutant strain Y-4, 178.7 g/L of L-lactic acid was produced with the molar yields of 178.7% to the substrate glucose.